Performance of a Pulse-Jet Filter At High Filtration Velocity II. Filter Cake Redeposition

Pulse-jet filter cleaning is ineffective to the extent that collected dust redeposits rather than falls to the hopper. Dust tracer techniques were used to measure the amount of redeposition in a pilot scale pulse-jet filter. A mathematical model based on experimental results was developed to describe dust transfer from bag to bag, redeposition on the pulsed bag itself, and migration to the dust hopper. Dust redeposition upon the pulsed bag increased markedly with increasing filtration velocity, whereas migration and redeposition on bags adjacent to the pulsed bag decreased. For high velocity pulse-jet filters to operate at lowest possible pressure drop, filter cake redeposition must be minimized.     

The effect of nitrogen enrichment on the carbon sink in coniferous forests: Uncertainty and sensitivity analyses of three ecosystem models

Estimates of the global carbon sink induced by nitrogen enrichment range vary widely, from nearly zero to 2.3 Gt C year^?1. It is necessary to reduce this uncertainty if we are to make accurate predictions of the future magnitude of the terrestrial carbon sink. Here, we present a Monte Carlo approach to uncertainty and sensitivity analysis of three ecosystem models, Century, BGC and Hybrid. These models were applied to a coniferous forest ecosystem in Sweden. The best estimate of the change in total carbon content of the ecosystem with the cumulative change in nitrogen deposition over 100 years, ΔC_total/ΔN_deposition was 20.1 kg C (kg N)^?1 using the pooled mean, with a pooled standard deviation of 13.8 kg C (kg N)^?1. Variability in parameters accounted for 92% of the total uncertainty in ΔC_total/ΔN_deposition, and only 8% was attributable to differences between models. The most sensitive parameters were those which controlled the allocation of assimilate between leaves, roots and stem. In particular, an increase in allocation to fine roots led to a large reduction in ΔC_total/ΔN_deposition in all models, because the fine roots have a very high turnover rate, and extra carbon allocated there is soon lost through mortality and decomposition.     

Coping with advanced manufacturing technology

Computer aided manufacturing equipment is supposed to revolutionize batch production by increasing control over this highly uncertain mode of manufacturing. However, as computerized equipment becomes more complex it becomes less compatible with the socio-technical systems of most firms. The ensuing problems, with which management, staff specialists and workers have great difficulty in coping, lead to the new technology being only partially under control. It is difficult to evaluate whether to purchase a computerized manufacturing system and there are problems in evaluating their efficiency once they are implemented. Evidence is presented from case studies of five firms in three nations that have purchased computerized production systems. Policy recommendations and research suggestions are provided for dealing with the situation.     

Cleaning of Stack Gases Containing High Concentrations of Nitrogen Oxides

Multistage gas absorption of 1–50% nitric oxide, nitrogen dioxide, and nitrogen tetraoxide from air with water or caustic solutions can produce colorless stack discharges. The rate at which NO is oxidized to No₂ in the gas phase and the solubility rate of No₂ in water or solution are highly concentration dependent so that reductions of stack gas concentrations of nitrogen oxides below approximately 200 ppm appear to be impractical. High efficiency absorption combined with elevated discharge of the cleaned, colorless gases is an acceptable method of air pollution control for many troublesome operations. Experiences in the fields of rocketry and nuclear energy are cited. Engineering modifications of metal pickling operations have been found especially helpful in producing effective control at an acceptable cost.     

Control of Odors and Aerosols from Spent Grain Dryers

The information contained in this paper is directed to research workers concerned with odor identification and the development of methods for removal of odorous components from hot, moist stack gases and to application engineers faced with the practical problem of selecting effective, yet economical, odor control equipment for industrial operations. The new techniques described here demonstrate the beneficial uses of gas phase reactions as a conditioning step preceding absorption in a chemically reactive solution. Cost comparisons show markedly lower costs for full-scale reactor-absorbers than for gas incinerators for equal contaminant removal. Other methods of removing odors at the source, e.g., injection of ozone, use of nonvolatile oxidizing agents in solution, and adsorption on activated charcoal, were found to be impractical, ineffective, or both. The application of reactor-absorbers to spent grain drying is discussed in detail and reference is made to the use of this technique for other food industry waste treatment processes including rendering and fish and poultry meal production.     

New Kinds of Fabric Filtration Devices

New kinds of fabric filtration devices are reviewed in this paper. The industry is on the threshold of a period of innovation and development in this field which should see the advancement of new concepts of the way filters function.     

Effectiveness of Odor Counteractants for the Treatment of Stack Gases

Successful control of some contaminant sources is extremely difficult to achieve technically and there remains a need for more information specific to control procedures. The cost of air cleaning equipment installations can be exceedingly high depending upon the performance standards to be satisfied and the physical and chemical characteristics of the contaminants. Control of emissions from the foundry cupola, the steel mill, metal refining operations, coal burning utilities, and incinerators still presents imposing cost and operational and performance problems—despite the technological progress made in recent years. The interrelationship of the source, the degree of control necessary, the equipment available to do the job, and the costs are discussed.